There is more research into supersonic and
hypersonic flight happening now than ever
before. It is being driven by industry demand
to develop a supersonic passenger jet. Everyone
wants to fly faster.
To a certain extent, supersonic aircraft are still
developed through trial and error. Researchers use
wind tunnels and direct numerical simulations to
replicate flight conditions and solve turbulence
problems. If we want to reliably fly passengers at
supersonic and hypersonic speeds we need to
increase our understanding of airflow at these
speeds. Computer simulations have a key role to
play in achieving this.
However, the existing Navier Stokes equations
used to work out air flow at supersonic and
hypersonic speeds are inadequate and result in
inaccuracies. My research is improving the
accuracy of high-speed aerodynamics both
numerically and theoretically. It is using new
theoretical approaches and taking advantage of
the power of high-performance computers (HPCs).
The work will enable aerospace engineers to
design the next generation of supersonic and
hypersonic aircraft more efficiently and will help
silence sonic booms.
James Chen from the University at
Buffalo, the State University of New York,
simulations predict air flow at high speeds
My background is as an engineering scientist
and applied mathematician. I’ve worked in the field
of continuum physics and partial differential
equations, particularly fluid dynamics, for eight
years. When initially considering supersonic and
hypersonic flight, I soon realized the deficiencies
of using Navier Stokes to solve turbulence
problems and that we needed another way to work
out the behavior of air flow at these speeds.
I went back to the classical Kinetic Theory, first
developed by Austrian physicist Ludwig Boltzmann
in the 19th century. This deals with the gas
molecules, allowing us to look at the molecules in
the atmosphere and use the Maxwell–Boltzmann-
Curtiss distribution to devise another set of
equations to more accurately simulate airflow
at these speeds.
Once the approach had been developed, the
first and most important task was to show it works.
Theoretically and numerically we have achieved
this, with several peer-reviewed papers published.
We’ve proved out the equations and compared
simulations to experimental data from supersonic
wind tunnels. We’re confident that it is accurate.
Supercomputers are key to the research, they
are our screwdrivers and spanners. We use
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is improving the way computer
several supercomputing centres across the US.
The research team has access to around 200
cores, at the University at Buffalo and with the
US Air Force. But there is an important role for
wind tunnels in the future. You can only simulate
things you know, but that might not be the full
story. An experiment can tell you about the things
that are missing. We have to validate until we get a
stable and complete simulation. Simulations and
wind tunnels need to co-exist.
The research will be used very soon by projects
like Lockheed Martin and NASA’s QueSST.
Engineering teams in those organizations are
already doing reduced-model testing of their
supersonic passenger jet and next year plan to
have a full-sized model available. There are also
several start-up companies that want to develop
commercial jets. I will be very surprised if we don’t
see the return of supersonic passenger aircraft to
It’s incredibly gratifying to see the research
applied. It’s a long journey from equations to actual
applications in the sky. The research is enabling
better and more accurate simulations, speeding up
the development and reducing the cost of
supersonic aircraft. \\